The role of DS-182 in protection of cellular damages induced by oxygen free radicals was studied in rat cardiac mitochondria. The changes of cardiac mitochondrial enzyme (cytochrome oxidase) and P/O, RCR were used as indices of mitohondrial injury. The experimental animals were divided into three groups: control group, injury group (Fe~(2+)+ascorbic acid), and protection group (DS-182+Fe~(2+)+ascobic acid). Results obtained showed that incubation of mitochondrial suspension with ascorbic acid and Fe~(2+) resulted in decrease of activity of cytochrome oxidase, P/O (with ?-ketoglutarate andsuccinate as substrate respectively) and RCR, which indicated that the structure and function of mitochondria were damaged. Danshensu (DS-182) can inhibit the decrease of cytochrome oxidase activity, P/O and RCR. Thus, DS-182 with acts as an effective scavenger for oxygen free radicals prevented the mitochondrial injury.